Windows support

[veewee]

GrumPHP is not working on Windows CLI. This is because composer installs bat files for every bin file.
Some actions need to be taken:

• Remove the 'php' prefix in all process builders
• Make sure every processbuilder uses the external CommandLocator
• Check the OS in the CommandLocator and add .bat to the command if it is windows
• Possibly there is also a path problem. Windows uses the backslash as directory separator, and unix uses the frontslash.

Extra installation checks:

• We need to check if there is a git executable available. This could be handy in both windows as unix. If there is no git executable, an error message needs to be displayed and GrumPHP won't be hooked. Maybe we could take a look at the composer files to see how they resolve the git exectuable in windows.
• We assume the php executable is available, otherwise composer won't be able to install it's packages.

[veewee]

The GitElephant package does not support windows by default and has some issues:

• It uses the process builder incorrectly
• It can only find git executable on windows
• The status command does not recognice deleted and moved files

To make GrumPHP windows compatible, it might be better to use another git package.
At first sight, we might use: https://github.com/gitonomy/gitlib
It works with the process builder and has windows support.

[veewee]

Fixed in #8